A thyristor is a semiconductor device used as a switch in power control applications. Typically, thyristors are comprised of multiple layers of P-type semiconductor material and N-type semiconductor material. Various types of thyristors include, among others, triacs, silicon controlled rectifiers (SCRs), sidacs, and diacs. These devices differ from each other in the number of layers of P-type and N-type semiconductor material and in the number of terminals. For example, a triac is a five layer semiconductor device that has three terminals, a silicon controlled rectifier (SCR) is a four layer semiconductor device that has three terminals, a sidac is a five layer semiconductor device that has two terminals, and a diac is a three layer semiconductor device that has two terminals. Because of the configuration of the P-type and N-type semiconductor materials, thyristors are comprised of a plurality of PN junctions. Each PN junction has a small junction capacitance associated with it. When a voltage is applied across the thyristor, a charging current, IC, flows through the junction. The amount of current IC is given by Equation 1 as:IC=C*(dv/dt)  Equation 1where:
IC is the charging current in amperes;
C is the junction capacitance in Farads; and
dv/dt is a measure of the switching capability.
The thyristor switches on when the current IC equals or exceeds the thyristor trigger current IGT. To protect against fast rising voltages, semiconductor component manufacturers typically include protection circuitry with the thyristor. The protection circuitry adds to the cost of the thyristor and limits the temperature range over which the thyristor can effectively operate.
Another drawback with thyristors is that they may have an unbalanced trigger current, IGT. Although trigger current unbalancing is exacerbated in thyristors made from thicker wafers, the use of thicker wafers is advantageous because they increase the blocking voltage ratings of the thyristor.
Hence, a need exists for a thyristor having an improved switching capability with a balanced triggering current. Further, it would be advantageous for the thyristor to be cost efficient to manufacture.